The present invention relates to antifog films useful for packaging food, and more particularly to printed antifog films having an improved ability to maintain antifogging characteristics after being rolled.
Refrigerated food items are often displayed to consumers by resting the food item in a tray and covering the top of the tray with a transparent plastic film wrap. Typically, the food tray will have a perimeter lip extending above the stored food item so that the plastic film covering the top of the tray does not touch most of the packaged food. In this arrangement, the consumer may see clearly through the plastic wrap to view the food item stored in the package.
Upon refrigeration of a food item packaged in this manner, a “fog” may form on the inner, food-contact or food-side of the film, especially if the packaged food item has a high-moisture content. The term “fog” describes the collection of small moisture droplets that condense on the inner side of the film wrap. Unfortunately, these water droplets may cloud the inner surface of the film and thus obstruct or disrupt the view through the film—resulting in a negative consumer perception because of the inability to see clearly the packaged food through the plastic film wrap.
There have been several approaches to reduce the negative effects of fogging. One approach involves dispersing one or more antifog agents in the plastic film resin during processing of the film. Once in the film resin, the antifog agent tends to migrate to the surface of the film and raise the surface tension of the film. As a result, the water on the film inner side tends to form a relatively continuous film-like, transparent sheet of water rather than a fog.
Another approach to minimize the negative effects of fogging on a film involves applying an antifog coating directly to the plastic film's inner, food-side surface. Although this approach adds the expense of an additional coating step, it provides the benefit of applying the antifog agent to the film surface where it is most effective at reducing fogging.
A plastic film wrap typically includes printed images on regions of the film's outer surface to provide the consumer with visual information. Ink is printed to the outer, non-food side of the film to avoid contacting the packaged food with the print ink.
For the convenience of the packager, anti-fog packaging films are often supplied in pre-printed roll form. When the printed film is helically wound about a central core in progressive layers to form a roll, the printed side of the film contacts the non-printed side of film. This rolled arrangement causes surface contact between the film's printed outer side and the film's non-printed inner side. This contact appears to reduce the antifog effectiveness of the antifog film in the areas where the inner, food-side surface of the film has contacted the printed region of the film's outer surface.
As a result, when a packager unrolls a printed antifog film, wraps a food tray containing a food product, and refrigerates the packaged food product, a fog may form on the inner side of the film corresponding to the area of the inner surface that had been in contact with the printed region of the outer film surface when the film was rolled. Yet, where the film's inner surface area did not contact the printed regions when the film was rolled, the antifog film appears to function as designed—that is, reduces the formation of fog. The term “ghosting” refers to this contrast between transparent areas in which the antifog functions as designed and the opaque area in which a fog forms—because the fogged area on the film's inner surface may form a “ghost image” of the printed area on the film's outer surface.